水下通气超空泡航行体结构屈曲可靠性分析

STRUCTURAL BUCKLING RELIABILITY ANALYSIS OF UNDERWATER VENTILATED SUPERCAVITATING VEHICLES

在水下一定深度处高速运行的超空泡航行体,其所受轴向力非常大,同时受通气空泡环向压力,容易发生结构屈曲问题。考虑到结构自身参数和通气空化数的不确定性,有必要对航行体舱段结构进行屈曲可靠性分析。该文将航行体环向加肋舱段简化为变厚度圆柱薄壳,运用半解析有限元求解临界屈曲载荷系数,并采用随机有限元与有限步长迭代法相结合求屈曲可靠性指标。算例结果表明:屈曲可靠性指标随环肋个数增加而有较大增幅且在两端简支条件下受面内轴向约束影响较大,并随航行深度的增大呈下降趋势。控制薄壳厚度、弹性模量和环肋厚度的不确定程度可提高屈曲可靠性指标,而通气空化数的不确定程度变化对屈曲可靠性指标影响较为复杂。

When supercavitating vehicles cruise deeply under water with high speed, they will undergo high longitudinal force and circumferential pressure caused by ventilated cavity, which may result in structural buckling. The uncertainty of structural parameters and the ventilated cavitation number should be considered by performing structural buckling reliability analysis of vehicle compartments. The vehicle compartment with stiffening rings is simplified as thin cylindrical shell with variable thickness, and then the critical buckling load coefficient is obtained by semi-analytical finite element method. Buckling reliability index is obtained by hybrid method of stochastic finite element and limit step length iteration method. Numerical results show （1） buckling reliability index increases greatly with the increase of the ring number and it is mainly affected by the axial constraint if both ends of the compartment are simply supported, （2） buckling reliability index declines with the increase of operation depth and can be enhanced by controlling the uncertainty of thin shell thickness, elastic modulus and stiffening rings thickness, and （3） it is complex how buckling reliability index is affected by the uncertainty of the ventilated cavitation number.